Currently, electrodeionization (EDI) systems are implemented with a multiplicity of alternating anion and cation selective membranes, and mixed bed ion exchange resins such as EDI systems described U.S. Pat. No. 2,815,320. For this system, EDI cells were exclusively used for high purity water generation. The development of ion exchange membranes, described in U.S. Pat. No. Re. 24,865, rapidly led to the development of conventional, high-performance EDI systems as described in U.S. Pat. Nos. 4,632,745 and 4,465,573. These conventional EDI systems are merely adapted to purify reverse osmosis permeate in order to generate high purity water for the power, electronics and semiconductor industries.
However, there are a number of disadvantages associated with the current usage of conventional EDI systems. For instance, conventional EDI systems require low level concentrations of ionic load in the feed stream. Elevated concentrations can cause fouling of the EDI cells by depositing an unwanted layer on an outer surface of a resin or membrane of the conventional EDI system and may require very frequent chemical cleaning and regeneration. Second, conventional EDI systems are exclusively used in an indirect manner for purification of reverse osmosis permeate with low total dissolved solids (TDS) levels such as salts. EDI systems neither have been designed nor have been used directly to handle hazardous chemicals.
Therefore, it is contemplated that modification of the operations of the EDI system may enable new applications for using EDI other than for purification of reverse osmosis permeate.